This is a multicenter, randomized, double-blind trial of ZDV (180 mg/m3 q6h) versus ddI (120 mg/m2 q12h) versus a combination of ZDV and ddI to evaluate the safety, tolerance and efficacy of the treatment arms. All drugs will be administered orally. Approximately 600 HIV-infected symptomatic children between the ages of 3 months to 18 years will be enrolled into this study nationwide.